In recent years, with the trend of nonstop operation of a computer system, the importance of data backup is indispensable for a safe operation of the computer system. Consequently, various methods for performing data backup have been proposed.
For example, Japanese Patent Application No. 5-81147 discloses an automatic saving and restoring method for a volatile storage. The method detects whether a residual capacity of exists power in a power supply by a residual capacity detector and transfers the contents of the volatile storage to a non-volatile storage when the residual capacity is equal to or lower than a predetermined level. Japanese Patent Application No. 5-120110 discloses an automatic backup system for a file. The system performs data backup of a file which has been previously designated when communications via a Local Area Network (LAN) is not heavy. Japanese Patent Application No. 6-4223 discloses a disk copying system for executing a disk (storage medium) copy from a device suspected to have failed to another device when the copying is judged to be necessary due to the identification of the device suspected to have failed. Japanese Patent Application No. 6-139027 discloses a data backup technique for a disk array system. In a configuration having multiple disk drives becoming a disk array, spare drives, and a backup device are provided and controlled by a disk array controller. The spare drive is used as a data transfer buffer when transferring data transfer from the disk drives to the backup device. Japanese Patent Application No. 6-168080 discloses a technique for preventing old backup data from being erroneously used by recording the latest data update time and backup completion time when data backup for each of main and spare disks is performed in a data backup system. Thus, this technique in accordance with a setting of a switch by a job terminating program, the latest data update time and the backup completion time are collated with each backup from either the main or spare disk. Japanese Patent Application No. 6-309209 discloses a file backup method which provides a flag area in a part of file management information for specifying whether an automatic backup is necessary or not with respect to a file to be stored in an auxiliary storage. Thus, a backup is automatically performed when the flag area in the file management information specifies that a backup is necessary. Japanese Patent Application No. 8-212142 discloses a data backup system for a database which performs a data backup using a backup control file and a history file. Japanese Patent Application No. 9-50394 discloses an automatic data saving system in which an automatic activating unit, a saving unit, and the like are provided in a computer to which a direct access storage and a magnetic tape device are connected. Data backup is performed by a job control statement requesting a saving process created by the saving unit. Japanese Patent Application No. 9-101912 discloses a differential backup method which performs differential backup by providing a differential managing mechanism for recording/managing a backup generation and the like for each block in an external storage as a part of the kernel in which an operating system exists. Japanese Patent Application No. 10-283121 discloses a data backup system which executes a data backup without using a CPU, main memory unit or a system bus by judging which one of the main memory unit and local memory access on a standard I/O bus is to be performed by a bus controller. Japanese Patent Application NO. 8-234916 discloses automatic backup system without occupying a host device. Japanese Patent Application No. 7-239759 discloses backup system recording information of the disk array. Japanese Patent Application No. 7-200191 discloses disk array device which have a timer. Japanese Patent Application No. 7-93101 discloses backup system without using a bus. Japanese Patent Application No. 4-311219 discloses backup system without interfering a host device.
The above described conventional techniques except those described in Japanese Patent Application No. 6-4223 and Japanese Patent Application No. 6-139027 have a disadvantage in that a load is applied to the host device since the data backup is executed by processing performed by the host device. The conventional technique described in Japanese Patent Application No. 6-4223 saves data in a device reserved against failures by a disk error collecting unit and a medium copying unit. Thus, this conventional technique has a disadvantage that a motive for data saving is limited to a time only when a device is suspected to have failed being that errors are anticipated to occur frequently. The conventional technique described in Japanese Patent Application No. 6-139027 has to obtain information such as application range of a file system from a host computer. Accordingly, the advantage is that backup cannot be performed automatically.